I want to make a set of card pictures for making a card game in Scratch (which probably won't have rules; any card may be moved anywhere, and will be aligned to some certain rounding numbers, and the FreeCell deal algorithm will be used) and, if you know me well, my favorite color scheme is yellow on black. The pictures are 60×81 (the reason for odd height is complex) and they use black, red and yellow, and are png. Setting the preview to large icons in Windows Explorer (Windows 10) will show them in accurate pixel size, but the Windows Thumbnails have jpg artifacts (the yellow and red colors look horrible on single pixel lines and on edges of suit shapes). This image demonstrates the issue:


  • I don't want to create vector images. I want to create bitmap pictures, with pixel precision. The issue is with Windows Thumbnails; the pictures themselves are fine. – Piotr Grochowski Jan 16 '18 at 10:28

Windows saves a small copy of any image as a compressed JPG in an hidden database (Thumbs.db in Windows XP and earlier, %userprofile%\AppData\Local\Microsoft\Windows\Explorer*.db in later versions)

Even if originally it was a pixel perfect PNG, Windows saves a jpg thumbnail of it, leading to artifacts.

This behavior is just visual aesthetic, the original files are still PNG, but for performance reasons, Windows doesn't actually open your file to see the thumbnail, but it uses the compressed one in its database.

Reference: https://en.wikipedia.org/wiki/Windows_thumbnail_cache

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